Masking of components and other areas of printed circuit boards is typically desirable to prevent damage and contamination of such components while the board is being further assembled, soldered, stored and/or transported. Existing masking methods include tapes, boots, dies, latex and solvent based masking materials which are applied to the areas to be protected and later removed for final assembly.
With tapes, boots and dies, care must be exercised to ensure that the desired area is properly protected and that such masks will not prematurely fall off during further processing. Solvent based masking materials are not desirable in many applications because of the hazardous emissions of such solvents, typically volatile organic compounds or VOS, and the possible adverse reactions of such solvents with a surface upon which they are deposited.
Hot-melt elastomeric adhesives have also been utilized as masking materials. Such adhesives easily adhere to and release from the surface on which they are deposited without leaving a residue thereon and without increased adhesion over time.
Existing methods of dispensing such adhesives, however, are not very effective in precisely dispensing adhesive onto smaller components. In view of the ever decreasing size of electrical components in many applications, precise dispensing has become a goal in the industry.
Existing systems, however, utilize a cumbersome, large hand gun which does not provide accurate dispensing or precise shut-off of adhesive on demand. Accordingly, proper masking of localized minute areas of a circuit board is simply not possible with these existing systems.
It therefore would be desirable to provide a system for pin-point injection or application of a viscous hot-melt conformal coating to localized minute areas of an article, such as an electrical component of a printed circuit board, which readily conforms to the surface of the component, cools quickly at room temperature and can be readily removed from the component to provide a temporary mask to the component so that the printed circuit board can be processed further without damaging or contaminating the masked component.